In fact i was only querying, but when i add many items in the same
flush, all items(of same category)get the same value, and i don't know
how to include the sku number already calculated to the query, that's
the reason because i tried this approach of saving "last_sku_value",
but i sow that something was really bad.
I tried to execute the query on __init__() of my class but i had to
pass the session to my object or take my session from a global so i
thought it was a bad idea.
And i could create my object add it to my session and after call a
function "class.new_sku()", but i dislike the idea to rewrite this for
each item.
this is my "get_last_value()" code, maybe it'll be clear:
def get_last_value(self, session, cls, instance):
"""execute a query to find the last value"""
try:
return self.last_value[instance.dynamic.value]
except KeyError:
self.last_value_key = "%s-%s" %(instance.dynamic.static,
instance.dynamic.value)
last_sku_value = session.query(cls.value)\
.filter(cls.dynamic == instance.dynamic)\
.order_by(desc(cls.date_insert)).first()
if not last_sku_value:
return None
try:
return last_sku_value[0]
except IndexError:
return None
On 13 jul, 16:35, Michael Bayer <[email protected]> wrote:
> On Jul 13, 2010, at 10:21 AM, sacabuche wrote:
>
>
>
> > I was trying to get the last value "before_insert" a new item but i
> > didn't find out, so i change of strategy and i saved the last value of
> > this method, but the problem is that when i do other commits my old
> > MapperExtension attribute (self.last_value) get the last value and i
> > dislike it, even when I close and open a new Session (discovered in my
> > tests)
>
> > This is my code:
>
> > class _ValueExtension(MapperExtension):
> > """Set new value for SkuDynamic and SKuUnique"""
> > def __init__(self):
> > self.last_value = {} # <<--- THE PROBLEM
> > self.first_value = FIRST_VALUE
>
> > def before_insert(self, mapper, connection, instance):
> > session = object_session(instance)
> > cls = instance.__class__
>
> > last_sku_value = self.get_last_value(session, cls, instance)
>
> > if not last_sku_value:
> > instance.value = self.first_value
> > else:
> > instance.value = next_value(last_sku_value)
>
> > self.last_value[self.last_value_key] = instance.value
> > self.set_values(instance)
>
> > #def after_insert(self, mapper, connection, instance):
> > # self.__init__() #<--- IF I DO THIS I DON'T HAVE THE LAST
> > VALUE IN THE SAME FLUSH
>
> > #def after_update(self, mapper, connection, instance):
> > # self.__init__()
>
> > def get_last_value(self, session, cls, instance):
> > """This have to return just one value
> > and set self.last_value_key is nedded to update elements in same
> > session
> > Execute The Query or check self.last_value
> > """
> > raise NotImplementedError, 'implement this function'
>
> > def set_values(self, instance):
> > """Use if necesary"""
> > pass
>
> A MapperExtension is persistent for the life of the application and also is
> accessed concurrently, so it is not an appropriate place to store a count for
> things things that are local to a specific flush, and its really not a good
> place in general to do what you're trying to do (though its not clear above
> what you're trying to accomplish, if you want a global "last sku" or a "sku"
> specific to one flush).
>
> You'd be better off querying the database for the "last sku value" when you
> need it, or just adding code to your classes __init__() method to keep track
> of sku numbers in memory as needed.
>
>
>
> > Thanks
>
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>
>
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